Magnetic damping or drag means utilizing permanent or "hard" magnets have for some years been used with instruments containing rotatable electroconductive disk armature members driven by electromagnetic flux fields such as integrating watthour meters for measuring the rate of flow or utilization of electrical energy. Magnetic damping or drag means in such instruments, as is well known, dampen or retard, and govern the speed of rotation of the disk armature. The disk speed results from the force produced within the disk by interacting flux fields generated by induction magnets which are activated by the voltage and the current in the circuit being measured.
The prior art provides many examples of various types and systems of magnetic damping means for electromagnetically driven disk armatures in induction watthour meters, and details their mechanisms and operations. For example, U.S. Pat. Nos. 2,110,418, 2,595,244, 2,196,898, 2,668,275, 2,272,748, 2,683,921, 2,316,638, and many others. The contents of the foregoing cited U.S. patents are incorporated herein by reference.